JPS631189A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a good color video signal which has less deterioration of resolution and color bleeding etc. by providing the first and the second filters which can be controlled and executing an ideal filter processing to a chrominance signal converted in a low pass and a frequency-modulated luminance signal. CONSTITUTION:Input video signals are distributed to a luminance signal processing system 2 and a chromaticity signal processing system 7. According to deciding whether the voltage difference vY--vC which is a difference between the down side band wave level vY of an FM luminance signal that is the output of a BPF 4 and a detector 5 and the high pass side band wave level vC of a low pass conversion chromaticity signal that is the output of a BPF 9 and a detector 10 is higher than a previously specified threshold voltage or lower than that, a control circuit 6 controls the cut-off frequency of an HPF 30 and an LPF 80 and executes an ideal band limiting (filter processing) to the FM luminance signal and the low pass chromaticity signal. The band-limited FM luminance signal and the low pass chromaticity signal are mixed in a mixer 11 and recorded on a magnet tape by a magnet head 13 through a record amplifier 12.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a magnetic recording/reproducing apparatus that records a low frequency converted carrier color signal together with a luminance signal.

2. Description of the Related Art Conventionally, in home video tape recorders, a method has been established in which a low frequency-converted carrier color signal is recorded on a magnetic tape together with a frequency-modulated luminance signal, the so-called color under recording method (for example, , Edited by the Television Society of Japan, "Introduction to Home VTR JPP, 28-41) O Figure 3 shows the main blocks on the video signal recording side of a general color under type video tape recorder. In the figure,
A video signal to be recorded that has entered the input terminal 1 is distributed to a luminance signal processing system 2 and a chroma signal processing system 7. In the luminance signal processing system 2, as is well known, the luminance signal components are separated and subjected to luminance signal processing such as pre-emphasis, white clipping, dark clipping, etc., and then a frequency modulator is used to convert the video signal into a sync chip. The level and white peak level are each set to a predetermined frequency (for example, sync tip is 3.4LIIk, white peak is 4.4M).
) is frequency modulated so that The frequency-modulated luminance signal (hereinafter abbreviated as FM luminance signal) has FM sidebands spread over a wide band as shown in C in Fig. 4, so it has high frequency characteristics as shown in B in Fig. 4. Filter (H
After the lower band components included in the FM luminance signal are band-limited in the PF 3, they are mixed with a low frequency converted chroma signal (hereinafter abbreviated as low frequency converted chroma signal) in the mixer 11.

- On the other hand, in the chroma signal processing system 1, as is also well known, the chroma signal component is separated from the video signal, and a balanced modulator is used to divide the chroma signal component into a predetermined frequency (for example, 629 klb).
The low range is converted to . The low-pass converted chroma signal (see Figure 6) is band-limited by a low-pass filter (LPF) whose characteristics are as shown in A in Figure 4, and then passed through the mixer 1 described above.
1 and mixed with the FM luminance signal. The low frequency converted chroma signal mixed with the FM luminance signal is amplified to a predetermined recording level by a recording amplifier 12 or the like, and then recorded on a magnetic tape by a magnetic head 13.

As described above, in a color under type video tape recorder, the low frequency converted chroma signal and the luminance signal are frequency-multiplexed and recorded, and the band is limited by HPF3 and LPFs to prevent both signal components from interfering with each other. It is carried out.

Problems to be Solved by the Invention However, by limiting the FM luminance signal band by HPF3, the recording band of the luminance signal is limited, and in the end, the reproduced luminance signal band can only be reproduced up to the band limited by HPF3. It turns out you can't do it. This is due to insufficient consideration of the reproduced image), and the deterioration of detail reproducibility9.
Problems such as characters not being scratched occurred.

Furthermore, if the band of HPF3 is widened in order to solve the above problem, interference between the low frequency converted chroma signal and the FM luminance signal will occur, resulting in beat interference, cross color interference, etc. In this case, the band of LPF8 will be increased. Therefore, the chroma signal band becomes narrow, and color fringing becomes noticeable on a screen with a high degree of color saturation.

In view of the above problems, the present invention performs suitable filter processing on the FM luminance signal and the low-frequency chroma signal by detecting the lower sideband level of the FM luminance signal and the high-frequency sideband level of the low-frequency converted chroma signal. Thus, the present invention aims to provide a magnetic recording and reproducing device that can reproduce high-quality color video signals.

Means for Solving the Problems In order to solve the above problems, the magnetic recording and reproducing apparatus of the present invention separates a color video signal into a luminance signal and a color subcarrier by a frequency separation means, and frequency modulates the luminance signal. , a helical scan type magnetic recording and reproducing device that converts the color subcarrier into a low frequency band for recording, detects the amplitude level of the lower sideband component of the frequency-modulated luminance signal, and detects the amplitude level of the lower sideband component of the frequency-modulated luminance signal. a first detection circuit configured such that the output voltage is high when the amplitude level of the lower sideband component is high, and the output voltage is low when the amplitude level of the lower sideband component is low; and the output voltage level of the first detection circuit. When the output voltage level of the first detection circuit is high, the cutoff frequency is lowered,
When the output voltage level of the first detection circuit is low, the filter is called a low-pass filter that is configured to limit the band of the color subcarrier converted to a low frequency by setting the cutoff frequency high. It has a configuration.

According to the above-described configuration, when the FM luminance lower sideband level near the low-frequency converted chroma signal band is higher than the high-frequency sideband level in the low-frequency converted chroma signal by more than a predetermined threshold level, In other words, when there are many high-frequency luminance components and few high-frequency chroma components in the video signal, the lower band of the FM luminance signal is extended to the lower frequency range, and at the same time, the band of the low-frequency converted chroma signal is narrowed using a filter. Limit to bandwidth.

Conversely, if the high sideband level in the low frequency converted chroma signal is higher than the predetermined threshold level compared to the FM luminance lower side band level near the low frequency converted chroma band, that is,
When there are many high-frequency chroma components in the video signal and few high-frequency luminance components, the band of the low-frequency converted chroma signal is wideband, and F
The band of the M luminance lower sideband is limited to a narrow band by a filter.

In this way, by performing filter processing on the low-frequency converted chroma signal and the FM luminance signal in a manner adapted to various forms of video signals, a screen with a low chroma signal level and a high high-frequency luminance level can be created. This will make the color lighter and
For screens that require high resolution, it is possible to suppress resolution deterioration of the luminance signal, and conversely, for screens that have a high high-frequency chroma signal level and a low high-frequency brightness level, in other words, nine colors are dark and the color A screen with sharp changes in level and hue.

With this method, it is possible to suppress deterioration of color resolution, color bleeding, etc., and thereby it is possible to reproduce a high-quality color video signal with little resolution deterioration and color bleeding.

Example Below, regarding a magnetic recording and reproducing device according to an example of the present invention,
This will be explained with reference to the drawings. FIG. 1 shows the main part of the recording side circuit in the first embodiment of the present invention, and FIG. 2 is an explanatory diagram thereof.

First, in FIG. 1, the video signal to be recorded that has entered the input terminal 1 is sent to the luminance signal processing system 2 and the chroma signal processing system 7.
As mentioned above, the luminance signal processing system 2 performs luminance signal processing such as luminance signal separation, pre-emphasis, white clipping, dark clipping, frequency modulation, etc., and the chroma signal processing system 2 performs chroma signal separation, balance modulation, etc. chroma signal processing is performed.

Next, the brightness signal (FM brightness signal) frequency-modulated to a predetermined frequency by the brightness signal processing system 2 is processed by the HPH30 and BPF.
4. BPF4 is a filter whose pass band is around the frequency where the low-frequency chroma signal and the FM luminance signal are superimposed (for example, around the shaded area in Fig. 4).
This is for extracting the lower side band components near the low chroma band in the luminance signal. The FM lower sideband component extracted by the BPF 4 is supplied to the control circuit 6 after the FM lower sideband level is detected by the detector 5 . Further, the carrier ROMA signal (low-frequency converted chroma signal) that has been low-frequency converted to a predetermined frequency by the chroma signal processing system 7 is supplied to the BPF 9 and the LPFs. The BPF 9 has the same or similar passband as the BPF 4 described above, and is used to extract high frequency sideband components (for example, the shaded area in FIG. 4) from the low frequency chroma signal. The low frequency chroma sideband component extracted by the BPF 9 is level-detected by a detector 1o and then supplied to the control circuit 6. The control circuit 6 controls HP according to the sideband level Vy of the FM luminance signal output from the detector 5 and the high sideband level Vc of the low frequency chroma signal output from the detector 1o.
This is for controlling F30 and LPFB0. Here, HP F 30 and LPFso are H as described in the conventional example.
P F 3 is equivalent to LPFB, but the difference is that the frequency characteristics can be controlled by the control circuit 6. The frequency characteristics of HPF 30 and LPFB 0 are controlled by the output voltage VY of the detector 5 and It is controlled by the voltage difference 'Vy-Vc with the output voltage Vc of the detector 1o, and 'Vy
-'Vc is higher than a predetermined threshold voltage, that is, if the sideband level of the FM luminance signal exceeds the predetermined threshold level compared to the high frequency sideband level of the low frequency chroma signal, the cutoff frequency of HPF30 fH is set to less than the conventional value, and the cutoff frequency DfL of the LPFso is set higher than the conventional value [Fig. 2 (B
)]. As a result, when recording a video signal in which the luminance signal has many high-frequency components and the chroma signal has few high-frequency components, it is possible to make the luminance signal band wider than before.

Conversely, when the voltage 'Vy-Vc between the output voltage Vy of the detector 6 and the output voltage vc of the detector 10 is lower than the threshold voltage, that is, the sideband level of the FM luminance signal is higher than the high-frequency sideband of the low-band chroma signal. If the wave level is below a predetermined threshold level, the cutoff frequency fH of the HPF 30 is set higher than before, and the cutoff frequency fL of I, PFso is set lower than before [Figure 2 (C)] ]
. As a result, when recording an image signal in which the luminance signal has few high-frequency components and the chroma signal has many high-frequency components, it is possible to make the band of the chroma signal wider than before.

In this way, by controlling the cutoff frequencies of Q2HPF30, I, and PF30 in a manner that adapts to the format of the video signal to be recorded, suitable band limiting (filter processing) can be performed for the FM luminance signal and the low-frequency chroma signal. Can be done. What are the band-limited FM luminance signal and low-frequency chroma signal?
After being mixed in the mixer 11, the signals are amplified to a predetermined recording level in the recording amplifier 12 described in the conventional example, and then recorded on the magnetic tape by the magnetic head 13.

As described above, according to the present embodiment, by performing filter processing adapted to the video signal, the luminance band is adjusted.

The chroma band can be improved compared to the conventional method.

Although the recording side circuit has been described in this embodiment, the reproduction side also has an HPF 30. It can be configured using LPFso, and by performing filter processing adapted to the above-mentioned video signal format in the recording/reproducing system, it is possible to obtain a high-quality color video signal with less resolution degradation and less color blurring than before. Note that the HPF30 and LPFso used in this example are filters whose cutoff frequencies can be controlled by a control voltage, and this configuration method is based on a combination of an LC filter and an active element, or a gyrator. What I used,
Various methods are possible, such as using a digital filter, but any filter whose cutoff frequency can be controlled may be used here.

In addition, in this embodiment, HPFsO and LPFso are controlled by detecting both the lower side band level of the FM luminance signal and the low frequency converted chroma signal. HPF30 and LPF are detected by detecting the level of one of the converted chroma signals.
so may also be controlled.

Effects of the Invention As described above, the present invention provides a first detection circuit for detecting the amplitude level of a lower sideband component in a frequency modulated luminance signal, and a first detection circuit for detecting the amplitude level of a lower sideband component in a frequency modulated luminance signal, and a first detection circuit for detecting the amplitude level of a lower sideband component in a frequency modulated luminance signal, and a second detection circuit for detecting all amplitude levels of sideband components;
By providing first and second filters that are controllable according to the level difference between the output of the detection circuit and the output of the second detection circuit, the low-pass converted carrier color signal and the frequency-modulated luminance signal can be combined. Appropriate filter processing is applied to the images, thereby producing high-quality color images with little resolution deterioration, color blurring, etc.
You can get the elephant signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the recording side of a magnetic recording/reproducing apparatus according to the first embodiment of the present invention, FIG. 2 is a frequency characteristic diagram for explaining FIG. 1, and FIG. 3 is a conventional magnetic recording/reproducing apparatus. FIG. 4 is a diagram showing the frequency characteristics of a conventional example. 4...BPF, s...Detector, 6...
...Control circuit, 9...BPF, 1o...
...Detector, 30...HPF. 8o...LPF. Name of agent: Patent attorney Toshio Nakao and one other person
- Figure 2 ft ft-t -, number of shoulders Figure 3 eyebrow M, number (MHz) procedural amendment form) July 1986/, 5"" a 2 Name of the invention Magnetic recording and reproducing device 3 amendment Relationship with cases involving persons who commit patent application Personnel Address: 1006 Kadoma, Kadoma City, Osaka Name (582) Representative of Matsushita Electric Industrial Co., Ltd.
Akio Tanii 4 Agent 571 Address 1006 Oaza Kabuto, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Date 7 of the amendment order, lines 10 to 11 on page 15 of the statement of contents of the amendment. "This is the recording side block diagram." will be corrected to "This is the recording side block diagram and frequency characteristic diagram."

Claims (4)

[Claims] (1) A helical scan type magnetic recording and reproducing device that separates a color video signal into a luminance signal and a color subcarrier using a frequency separation means, frequency modulates the luminance signal, and converts the color subcarrier to a low frequency band before recording. The amplitude level of the lower sideband component of the frequency-modulated luminance signal is detected, and when the amplitude level of the lower sideband component is high, the output voltage increases, and when the amplitude level of the lower sideband component is low, the output voltage increases. is controlled by a first detection circuit configured to have a low output voltage and the output voltage level of the first detection circuit, and when the output voltage level of the first detection circuit is high, the cutoff frequency is lowered. However, when the output voltage level of the first detection circuit is low, a low-pass filter is configured to limit the band of the color subcarrier converted to a low frequency by setting a high cutoff frequency. A magnetic recording/reproducing device characterized by having: (2) The first detection circuit for detecting the amplitude level of the lower side band component of the frequency-modulated luminance signal includes a low-pass or band-pass filter for extracting the lower side band component, and a low-pass filter for extracting the lower side band component; Alternatively, in order to detect the level of the output signal of the band-pass filter, if the output signal level of the low-pass or band-pass filter is high, the output signal of the detector becomes high; 2. The magnetic recording and reproducing apparatus according to claim 1, further comprising a detector configured such that the output signal of the detector becomes low when the output signal level of the detector is low. (3) A helical scan type magnetic recording and reproducing device that separates a color video signal into a luminance signal and a color subcarrier using a frequency separation means, frequency modulates the luminance signal, and converts the color subcarrier to a low frequency band before recording. If the amplitude level of the color subcarrier converted to a low band is high, the output voltage becomes high, and the amplitude level of the color subcarrier converted to a low band is detected. A second detection circuit is configured to output a low output voltage when the amplitude level of the carrier wave is low, and the output voltage level of the second detection circuit is controlled by the output voltage level of the second detection circuit. If the output voltage level of the second detection circuit is low, the cutoff frequency is set low.
1. A magnetic recording and reproducing device comprising a high-pass filter or a band-elimination filter configured to limit the band of a frequency-modulated luminance signal. (4) The second detection circuit for detecting the amplitude level of the color subcarrier converted to a low band is a high band or band pass for extracting the high frequency component of the color subcarrier converted to a low band. In order to detect the level of the output signal of the high-pass or band-pass type filter and the high-pass or band-pass filter, the output signal of the detector becomes high when the output signal level of the high-pass or band-pass filter is high. The magnetic recording and reproducing apparatus according to claim 3, further comprising a detector configured such that the output signal of the detector becomes low when the output signal level of the band-pass filter is low. .